Venous PO2 was measured in the feet and hands of four subject groups: 14 diabetics with neuropathy and foot ulceration; 12 diabetics with neuropathy but no ulceration; 11 diabetics with no evidence of microvascular complications; and 10 non-diabetic controls. Neither patients nor controls had clinical evidence of peripheral vascular disease. The mean venous PO2 in the feet of subjects with neuropathy and foot ulceration was significantly higher than in controls or the other two diabetic groups. Venous PO2 in the feet of the subjects with ulcers was also significantly higher than in their hands or in the hands of the other groups. These results provide further evidence of abnormal blood flow in the diabetic neuropathic foot and are compatible with arteriovenous shunting.